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Topic: Help with probability&stat problem
Replies: 47   Last Post: Jun 16, 2007 4:32 AM

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 Bruce Weaver Posts: 753 Registered: 12/18/04
Re: Help with probability&stat problem
Posted: Jun 11, 2007 4:03 PM
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tutorny wrote:
>> Think again. How would you work out the probability that exactly 30
>> left? See if your textbook has any examples like that.

>
> Hi Bruce, I have no clue. My book doesn't have anything even remotely
> close to this.
>
> If I want to get exactly 30, should I do p(x<=30.5) - p(x<=29.5),
> which will come to P(z <= 2.0261) - P(z <= 1.7878) = 0.9786 - 0.9631 =
> 0.0155. So, P(exactly 30 left the program) = 1.55%
>
> And, P(x<=30) = P(x<=29.5) + P(x=30) = 0.9631 + 0.0155 = 0.9786 =
> 97.86%

I didn't check your calculations, but notice that you already had the
0.9786 above as p(x <= 30.5). ;-)

>
> Does that make sense? I'm so confused!
>
> Thanks!

Using the binomial calculator at the link given below, I get p(x <= 30)
= 0.975286.... Your normal approximation is in the same ballpark.

http://stattrek.com/Tables/Binomial.aspx

--
Bruce Weaver
bweaver@lakeheadu.ca
www.angelfire.com/wv/bwhomedir

Date Subject Author
6/11/07 tutorny
6/11/07 briggs@encompasserve.org
6/11/07 tutorny
6/11/07 Randy Poe
6/11/07 tutorny
6/11/07 Bruce Weaver
6/11/07 tutorny
6/11/07 Bruce Weaver
6/11/07 C6L1V@shaw.ca
6/11/07 Randy Poe
6/11/07 tutorny
6/11/07 Nick
6/11/07 Jack Tomsky
6/11/07 Luis A. Afonso
6/11/07 Jack Tomsky
6/11/07 Luis A. Afonso
6/11/07 Jack Tomsky
6/12/07 Luis A. Afonso
6/12/07 Jack Tomsky
6/12/07 Luis A. Afonso
6/12/07 Jack Tomsky
6/12/07 Luis A. Afonso
6/13/07 Jack Tomsky
6/13/07 Luis A. Afonso
6/13/07 Anon.
6/13/07 Jack Tomsky
6/13/07 Jack Tomsky
6/13/07 Luis A. Afonso
6/13/07 Jack Tomsky
6/13/07 Anon.
6/13/07 Luis A. Afonso
6/13/07 Jack Tomsky
6/13/07 Jack Tomsky
6/13/07 Anon.
6/13/07 Luis A. Afonso
6/13/07 Jack Tomsky
6/13/07 Luis A. Afonso
6/13/07 Jack Tomsky
6/14/07 Luis A. Afonso
6/14/07 Luis A. Afonso
6/14/07 Jack Tomsky
6/14/07 Luis A. Afonso
6/15/07 Luis A. Afonso
6/15/07 Jack Tomsky
6/15/07 Luis A. Afonso
6/15/07 Jack Tomsky
6/15/07 Luis A. Afonso
6/16/07 Luis A. Afonso

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